Cheap 70-300mm lenses.

I'm pretty happy with my 50-200 lens, but would like a bit more 'reach', so have been considering going for a 70-300.

However, I don't have enough for the Pentax, so have been looking at the Tamron/Sigma offerings. Which are just within my budget.

I've rejected the Tamron as, going by the reviews and the sample images I've seen, it has pretty bad colour fringing at the long end.

Which leaves the two Sigmas. The APO model should be better, and most reviews say it is. However, I've seen one or two that suggest the improvement in CA is not that much and, in one review, that the non-APO one was marginally sharper at the long end.

Has anyone got experience of both and can advise on this?

The other option would be a 1.4x converter. SRS do a Kenko one for somewhat less than the Pentax one. Anyone used one? Are they any good, especially if used with the Pentax 50-200mm?

I know you've discounted it already, but I can't rate the 55-300 from Pentax highly enough. It's a great balance of image quality, size/weight and price. It would be best option, IMO, if you were able to save up for it.

Teleconverters are a mixed blessing. It really depends on the scenario you need more length in. The trade offs are less light hitting the sensor, any deficiencies in the lens are amplified and you obviously lengthen the wide end of the zoom, which depending on scenario could be detrimental.

If you want to go the teleconverter route, I have one I am about to offer for sale on the forum. That's because I just bought the Pentax HD one. The one I'm offering is a "Jessop" 1.7x which is af compatible.

here is a photo i took wjth the sigma 70/300 on my k5 at the weekend its the apo


dg


oh and by the way i have a spare one in the camera bag as well as that came with my k20

Stu, would that be the APO version or the other one?

Nice pic, BTW. Grey heron, if I'm not mistaken. We occasionally get them on the little tributaries that run into the Thames in Staines. Unfortunately, the last time I saw a heron, I only had my (Canon A1200) pocket camera with me, so I can't show the picture here. And the IQ is pretty bad - high ISO and a heavy crop!

Just to let everyone know that after further thought, some hours ruining my eye-sight gazing at sample images on the 'net and a quick look at the state of my credit cards, I ordered the non-APO Sigma DG Macro from SRS. The converter idea got rejected as it would lose a stop with the Pentax 50-200, would give slightly less extra reach and would cost slightly more.

It arrived late this morning and this afternoon got a quick test in our car-park. First impressions? Well, it's significantly bigger (and heavier - it weighs about the same as my K-S1 body) than the Pentax 50-200. The focus motor is a bit noisy (but quick) and the zoom barrel not exactly silky smooth.

Image wise, very good at the wide end, loses a bit of contrast at the long end and is also a bit less sharp there, possibly due to a small amount of fringing, though the fringing is only really noticeable with high contrast subjects. Macro looks good.

For the price, I think it's pretty darn good.


Oh, and I think I'm going to need a bigger gadget-bag!

SteveH

When I bought my 55-300 from SRS Ruislip (RIP!) I trialled it against the non-APO version of the Sigma 70-300 on my (then) GX-10 by focusing both on the tiles of the roof of a house on the opposite side of the road (about 70 (ish) metres away) - and the 55-300 was definitely sharper at the long end, and so I bought the Pentax!

OTOH, that was a long time ago (2008 IIRC) so maybe the latest version of the Sigma is better than the one I tested?